Descent of ManIn this lecture, beginners can familiarize themselves with basic information and terms used to describe the evolution of humanity beginning with the origin of primates through the comings and goings of Genus Homo.

The pain of rejection is more than mere metaphor. A team of scientists have found that to the brain, a social snub is just like stubbing a toe.

Brain scans carried out on volunteers showed that when they suffered a social snub, the brain's "pain centre" went into overdrive. The finding suggests that any emotional stress, such as the demise of a relationship or the loss of a loved one, might be far more closely linked to real pain than previously thought.

Scientists have known for some time that when a person is physically hurt, a part of the brain called the anterior cingulate flickers into action.

"It's like an alarm system. It lets you know when you're feeling pain," said Matthew Lieberman, a psychologist at the University of California in Los Angeles.

Dr Lieberman and his colleagues Naomi Eisenberger and Kipling Williams decided to see if the same part of the brain was triggered by emotional stress.

They got volunteers to lie down in a brain scanner while they played a simple computer game. The game involved hitting buttons on a handset to catch a virtual ball and then throw it to one of two other players on a screen.

Volunteers were told that the game was unimportant and that it was only being used to check that connections to the other players lying in scanners elsewhere worked. But the researchers were not telling the truth. The other two players were not real at all, but were being controlled by a computer program.

When the game started, all three players passed the ball around so that each got a fair share of the action. But after playing for a while, the computer-controlled players suddenly started throwing the ball only between themselves.

"We had people coming out of the scanners saying 'Did you see what they did to me!'," said Dr Lieberman.

The volunteers who felt most put out by the snub showed the biggest changes in brain activity. Their brain's "pain centre" had become far more active.

"The response to this social exclusion was remarkably similar to what you see in response to physical pain," said Dr Lieberman.

According to Dr Lieberman, his results should change how we think about emotional pain. "We tend to think physical harm is in a different category to emotional harm, but this shows we should be aware that emotional pain can cause the same kind of distress to someone as physical pain."

Professor Anthony Dickenson, of University College London, who specialises in the origins of pain, said: "This whole area is incredibly important because it's proving to the medical profession once and for all that emotional distress is a genuine thing, that people who are distressed and upset are not malingerers.

"It shows that the psychological aspects of pain are genuine and real and dealing with it is not a case of telling people to pull themselves together."

Dr Richard Wise, of Oxford University, who has used magnetic resonance imaging to study the effect of pain on the brain, said: "Studies like this have a broader value in that they can help us build up an idea of the networks in the brain that are involved in experiencing different feelings."